The related copending application, Ser. No. 08/754,916, whose contents, including the contents of the patents incorporated by reference in the said copending application, are herein incorporated by reference, describes apparatus for generating uniform magnetic fields in a region of interest employing wedge-shaped blocks as the primary generator of the main magnetic field. The copending application also describes supplying a high-permeability soft magnetic material member (referred to therein as a .mu.=.infin. material) positioned along one side of a magnetic structure comprising the wedge-shaped blocks, which has the effect of canceling the field on the back side of the high-permeability member thus concentrating the field on only one side of the structure. An important application for such apparatus is in magnetic resonance imaging (MRI) equipment for medical diagnosis, where a highly uniform magnetic field is essential to obtain high resolution images. As used herein, the term "uniform magnetic field" or "highly uniform magnetic field" means a magnetic field intensity H in a region of interest substantially satisfying the relationship (Hmax-Hmin)/Havg.ltoreq.10.sup.-4, equivalent to the field intensity H over the region of interest varying less than 100 ppm. As is explained in the copending application, when the wedge-shaped blocks satisfy certain magnetization and geometrical conditions, the desired uniform magnetic field will be realized when the blocks extend over a very large distance in the y and z directions of the arbitrary x,y,z coordinate system used to define the configuration of the magnetic structure. This is impractical in a usual implementation, and thus the blocks have to be shortened or truncated in the y and z directions. This action introduces distortions in the uniformity of the magnetic field in the region of interest. The copending application also describes one scheme for compensating such distortions using concepts described in a commonly-owned patent U.S. Pat. No. 5,495,222. Another commonly owned patent U.S. Pat. No. 5,428,333 describes another scheme for compensating for distortions in a uniform magnetic field produced by a magnetic structure based on the use of rectangular permanently magnetized blocks, in which a series of slits are introduced into the rectangular permanently magnetized blocks as the compensation means. This latter scheme cannot be used in a magnetic structure based on the wedge-shaped blocks of the present invention.